This invention relates to a combustion control system for an in-cylinder injection type of two-cycle engine and more particularly to an improved fuel injection system for an internal combustion engine and method for operating a fuel injection system for an engine.
In fuel injected internal combustion engines the injection strategy employed during starting is substantially the same as that during idle. That is, the fuel injection timing and duration during starting are generally the same as the injection timing and duration during idle. However, starting provides a different type of running characteristic than idle and the use of conventional injection techniques that employ the same fuel injection strategy for starting as at idle do not offer good starting characteristics. This is particularly true with two-cycle internal combustion engines.
As a basic reason why the same injection strategies do not offer good starting, there are certain characteristics of the engine that occur at starting which are true at idle. For example, when running at idle, generally the fuel injection is concluded at a very short time period before ignition occurs so as to insure that there will be a stoichiometric mixture present at the gap of the spark plug at the time of firing. However, during starting such retarded injection timing does not permit adequate fuel vaporization within the cylinder so as to insure combustion when the spark plug fires. Also, when injecting the fuel at a retarded period during starting, the fuel injection occurs at a time when the compression pressure is relatively high and the amount of fuel injected for a given time of opening of the injection valve may be reduced from that which occurs at idle operation.
It is, therefore, a principal object of this invention to provide an improved fuel injection system and method of operating a fuel injected engine that facilitates starting.
It is a further object of this invention to provide an improved starting fuel injection system and method of operation for a two-cycle internal combustion engine.
In conjunction with two-cycle internal combustion engines, it has also been proposed to provide an exhaust control valve which effectively changes the timing of opening and closing of the exhaust port while the engine is running. This permits the attainment of a high compression ratio to provide good fuel economy and emission control under low-and mid-range conditions and a reduced effective compression ratio under high speed running so as to avoid overheating and overloading of the engine. The exhaust control valve is positioned in its compression ratio raising position when in the idle operation. However, this gives rise to starting problems.
It is, therefore, a still further-object of this invention to provide an improved two-cycle engine exhaust control valve and operating system which will improve the starting of the engine without adversely affecting the performance of the engine under other running conditions.
There is another running condition of the engine which can also give rise to certain problems. This occurs when the engine is run at a rapid rate of speed that exceeds the normal speed at which the associated vehicle is being operated. This is a so called "racing engine" mode which commonly occurs. However, if the engine throttle valve is moved quickly to the idle position and the fuel control for the engine is also moved quickly to the idle condition, then uneven running and, in extreme cases, stalling may be encountered.
It is, therefore, a further object of this invention to provide an improved engine control which permits the engine to return to idle after a racing mode condition without stalling.